Numerous products require an efficient source of white light that is omnidirectional. In many applications, the desired output would be similar to the output of a conventional light bulb, the breakthrough invention of Thomas Edison, U.S. Pat. No. 223,898, issued Jan. 27, 1880. A host of products has been designed around the output taught by this historic invention. Recently, fluorescent-based light bulbs have been developed to mimic the output of the Edison bulb. Many inventors are trying to develop a bulb with a similar output that is based on LED technology. There are many shortcomings with the devices that have to date been developed.
One of the problems inherent in the use of LEDs for general lighting is the creation of white light from the narrow wavelength of light that is generated by an LED. Early examples of LED lighting systems relied on a combination of many different colored LEDs to create white light. In more recent examples, the output from a blue LED has been used to irradiate phosphor so that a broad spectrum of yellow light is radiated. The combination of the yellow light with some of the blue light that is not absorbed by the phosphor creates a reasonable white light source. In the prior art LED systems, the phosphor has typically been placed in close proximity to the blue LED so that all of the blue light passes on to the phosphor. However, newer inventions, such as U.S. Pat. No. 6,350,041, High Output Radial Dispersing Lamp, by Eric Tarsa, issued Feb. 26, 2002; U.S. Pat. No. 7,080,932, LED with an Optical System, by Matthijs Keuper, issued Jul. 25, 2006; and U.S. Pat. No. 7,080,932, Optical Manifold for Light Emitting Diodes, by Julio Chaves, issued Jun. 3, 2008; all teach the location of the phosphor at a distance away from the LED. All of these inventions have a generally efficient method of coupling the LED light to the phosphor.
Some of the prior art devices are more elaborate and therefore more expensive than others. None of the prior art inventions teach how to efficiently extract the light from the phosphor. Further none of the prior art inventions teach a light source that produces an omni-directional light output that is similar to the output of the original Edison invention.
Accordingly, it is an object of the present invention to provide an optical system that extracts a high percentage of the light generated by a phosphor source.
It is a further object of the present invention to effectively couple blue light from an LED to the light produced from irradiated phosphor.
It is a further object of the present invention to create all of the desirable optical qualities of the Edison lamp at a cost that allows mass deployment of energy efficient LEDs.